1. Field of the Invention
The present invention relates to a portable liquid crystal display device which uses a liquid crystal panel, and more specifically it relates to a support structure for a liquid crystal panel.
2. Description of the Related Art
A known type of liquid crystal panel is the passive liquid crystal panel which consists of a liquid crystal material sandwiched between two transparent substrates which are made of glass or film, with electrodes provided, on the opposing faces of the two substrates, so that they are mutually perpendicular, and the active liquid crystal panel, in which an electrode is provided on one of the opposing faces of two substrates, and a TFT thin-film transistor, MIM (metal-insulator-metal), or the like is formed on the other opposing face.
Liquid crystal panels can be classified in terms of operation as TN (twisted nematic) and STN (super twisted nematic) liquid crystal panels. The STN mode of operation is used in passive liquid crystal panels and the TN mode is used in both active liquid crystal panels and passive liquid crystal panels.
Active matrix liquid crystal display (LCD) panels are used as liquid crystal panels for a high-quality display. However, the active matrix LCD panels present the problem of the liquid crystal display device being high in cost. On the other hand, while TN passive liquid crystal panels are inexpensive, they are very inferior to active liquid crystal panels in terms of display quality.
In consideration of the above-noted types of liquid crystal panels, recent years have seen the appearance of commercial embodiments of a portable TV picture receiver, which consists of a compact, lightweight liquid crystal display device with a TV reception function, a liquid crystal projector, and a hand-held personal computer these products taking advantage of the benefits of liquid crystal panels. With this situation as the backdrop, there is a demand for compact, low-cost liquid crystal display devices.
The prior art will be described in connection with FIG. 5 and FIG. 6, which show a liquid crystal display device of the past. FIG. 5 is a perspective view which shows a simplified view of a liquid crystal display device of the past, and FIG. 6 is a cross-sectional view along the cutting plane A--A shown in FIG. 5. The construction of the liquid crystal display device shown in FIG. 6 is such that it includes, in sequence as seen from the display surface 13, a liquid crystal panel 10, an illumination device 20, a flexible printed circuit 40, and a circuit board 30 housed within a frame 50 which is supported by positioning member 51 provided on the frame 50. In FIG. 6, the approximately transparent protective board, such as a glass or an acrylic resin board which is positioned on top of the liquid crystal panel has been omitted.
The liquid crystal panel 10 is configured so as to have two opposing transparent glass or plastic material between which is sealed by means of a sealant a liquid material, and can also be constructed so as to further have a driving integrated circuit mounted, using the COG method, onto a board made of a glass or plastic positioned outside of the sealant for the purpose of driving the electrodes of the display element. The illumination device 20 is configured to have a fluorescent tube, a reflector which is positioned behind the fluorescent tube and which reflects the light of the fluorescent tube onto the liquid crystal panel 10, and a diffusing element which is positioned in front of the fluorescent tube and which diffuses the light.
In the past, active liquid crystal panels were used in making liquid crystal display devices, and a TN passive liquid crystal panel is used in the configuration shown in FIG. 6. As described above, however, active liquid crystal panels are expensive, and passive liquid crystal panels, while they are inexpensive, have greatly inferior display quality. For that reason, by using an STN passive liquid crystal panel a liquid crystal panel was achieved with a suitable balance between the above-noted cost and appearance.
An STN passive liquid crystal panel is less expensive than an active liquid crystal panel, and has better appearance than conventional passive liquid crystal panels. However, when using an STN passive liquid crystal panel in a liquid crystal display device, unwanted colors are imparted to the light which is transmitted through the liquid crystal panel, resulting in the discoloration of a black-and-white display screen. For this reason, a compensating element in the form of a compensation cell such as a compensation film or liquid crystal panel or the like is generally installed with the liquid crystal panel (hereinafter referred to a drive panel) to eliminate the above-noted discoloration.
When installing a compensating element on a drive panel as noted above, because the compensating element and the drive panel are directly overlaid in the frame 50 in manner similar to that shown in FIG. 6, a large number of positioning members are provided on the frame to position and support the drive panel and compensating element. Also, because the drive panel has either external circuit connecting terminals or a COG mounting area, the dimensions of the drive panel are larger than those of the compensating element, preventing the positioning of both the drive panel and the compensating element by means of common positing elements, making necessary a large number of positioners, this leading to, among other things, an increase in the complexity of the frame which has the positioners, thereby preventing the achievement of a sufficiently compact liquid crystal display device and causing an increase in the price of the product.
In addition, in a construction which is similar to that described above, because the drive panel and the compensating element are directly overlaid, when either the drive panel or the compensating element is broken, to remove the broken drive panel or compensating element, there is a risk of damaging the display surface of the good compensating element or drive panel, and vibration that is receive in transport and the like can also cause a skewing of the drive panel and the compensating element, which can damage them. Another problem is that because at least two liquid crystal panels are used supporting members for each liquid crystal panel are required, this causing an increase in the size of the liquid crystal display device.
Another problem is that the means to solve the above-noted problems makes the positioning of the above-noted drive panel and compensating element complex.